Abū Saʿīd, may Allah be pleased with him, reported that the Messenger of Allah, peace and blessings be upon him, said, “When you hear the call to prayer, repeat what the muezzin says.” Agreed upon by al-Bukhārī and Muslim.

Muslim also records from ʿAbd Allāh ibn ʿAmr, may Allah be pleased with them both, that he heard the Prophet, peace and blessings be upon him, say, “When you hear the muezzin, repeat what he says. Then invoke blessings upon me, for whoever invokes one blessing upon me, Allah will confer ten blessings upon him. After that, ask Allah to grant me al-wasīlah, for it is a station in Paradise befitting only one servant of Allah, and I hope to be that servant. Whoever asks al-wasīlah for me, my intercession will become permissible for him.”

ʿUmar ibn al-Khaṭṭāb, may Allah be pleased with him, said: “The Messenger of Allah, peace and blessings be upon him, said: ‘When the muezzin says, “Allāhu akbar, Allāhu akbar,” and one of you responds, “Allāhu akbar, Allāhu akbar”; then he says, “Ashhadu an lā ilāha illā Allah,” and you reply, “Ashhadu an lā ilāha illā Allah”; then he says, “Ashhadu anna Muḥammadan rasūl Allah,” and you reply, “Ashhadu anna Muḥammadan rasūl Allah”; then when he says, “Ḥayya ʿala-ṣ-ṣalāh,” you should say, “Lā ḥawla wa lā quwwata illā billāh”; and when he says, “Ḥayya ʿala-l-falāḥ,” you should say, “Lā ḥawla wa lā quwwata illā billāh”; then he says, “Allāhu akbar, Allāhu akbar,” and you respond, “Allāhu akbar, Allāhu akbar”; finally, when he says, “Lā ilāha illā Allah,” and you respond, “Lā ilāha illā Allah” from the depths of your heart—you will enter Paradise.’” Recorded by Muslim.